1. Field of the Invention:
The present invention is directed to the field of web transport mechanisms and more particularly to magnetic tape decks and improvements therein.
2. Description of the Prior Art:
Reel-to-reel type tape transport mechanisms, especially those which utilize tape cassettes, are subject to tape fouling. One of the causes of tape fouling, occurs when the tape drive mechanism is initially engaged with the tape and reels. The rotationally driven capstan engages the tape between itself and a biased pinch roller and pulls the tape across the tape head. A take-up reel is also rotationally driven, through a slip clutch, to take-up the slack in the tape after it passes from the capstan. However, at the instant of initial start-up, a loop often develops between the capstan and the take-up reel before the take-up reel has had a chance to remove all the slack in the tape between the reel and the capstan. Depending upon the slackness of the tape, and the lightness of the tape, the loop sometimes has sufficient inertia to instantaneously wrap around the capstan, become caught between the incoming tape and the capstan, and be wound thereon. When this capstan windup occurs, the clutch driven take-up reel reverses its direction of rotation, due to the tape being drawn therefrom and wound onto the capstan. The windup continues until it is either audibly detected and stopped by the operator or binds up the capstan/pinch roller mechanism.
When detected and stopped, the tape must be carefully unwound from the capstan by hand. However, in some cases, the woundup tape is folded and wrinkled so badly that it must be discarded.
In some cassette tape decks, such as those installed on automotive vehicles, the cassettes are inserted through an apertured panel and automatically engaged by the tape deck mechanism for playback. When the tape fully unwinds from its supply reel, except for its attached end, onto the take-up reel, the take-up reel stops rotating. A motion sensing mechanism and circuit causes the tape reel drive mechanism to stop and eject the cassette or reverse the play direction, depending upon the unit. In any event, the state of the art motion sensing mechanisms do not distinguish between the proper rotational direction accompanying normal operation and the reverse rotational direction of the take-up reel caused by capstan windup.